Operation
DA1855A-OM-E Rev A
ISSUED: July 2002
3-9
design and is intended to drive a 50
Ω
load. Without the load, the
filter's frequency response and transient response are altered.
1 MHz
— The 1MHz filter is of the same design as the 20 MHz
filter, and the same remarks apply.
100 kHz
— The 100kHz filter is an active filter with a 50
Ω
output
impedance. Transient and frequency response are independent
of the load impedance.
Overload
When a signal, which could damage the DA1855A, has been
applied to either input connector, the DA1855A protects itself by
disconnecting the signal. The input coupling mode changes to
OFF
, and the
OVERLOAD
light is turned on.
To reset the amplifier to normal operation, remove the offending
input, press any of the input coupling modes (
AC
,
OFF
, or
DC
).
The Overload light will turn off indicating the amplifier is reset.
When the
ATTENUATOR
is set to
÷÷
1
, an input signal of
approximately ±19 Volt will activate the overload protection
circuit. Fast transients will draw up to about 70 mA of input
current for a brief period before the input coupling relay acts to
disconnect the input.
Caution:
Inputs in excess of 250 Volt may cause permanent dam-
age to the DA1855A.
The input is not disconnected when the
ATTENUATOR
is set to
÷÷
10
. The input attenuator can withstand up to 200 Volt continuous
input.
REAR PANEL
Power
Normal instrument operation is obtained with the power switch in
the
1
(ON) position. The instrument can be used immediately,
however it requires a 30 minute warm up period to reach
specified performance. Prior to reaching operating temperature,
the amplifier offset will drift and the output from the Precision
Voltage Generator may not be within specification. In high-
humidity environments the time to stabilize may be much longer.
In high humidity environments or when warm-up time inhibits
